Correct Answer: Coal, Natural Gas and Petroleum

Solution : The correct option is Coal, Natural Gas and Petroleum.

Thermal power is produced mostly from coal, natural gas and petroleum. Thermal power generation or thermoelectric power generation is named to the process of generation of energy from steam. One of the most frequent forms of thermal electricity generation is coal-fired power stations. Natural gas-fired power stations are also commonly utilised to generate thermal electricity. Some power plants use petroleum as a fuel source.